This invention relates to apparatus for welding the seam of large diameter pipe, and particularly to an improvement in apparatus for spreading the seam edges preparatory to longitudinal movement of the pipe onto the arbor of the welding machine.
Devices are known for spreading the seam edges of pipe by permanent deformation prior to installation of the formed pipe on an outside diameter welding machine. A separate machine for this purpose is shown in U.S. Pat. No. 3,937,054 Hortvet. Probably more pertinent however, is the conventional means used in the past on some O.D. welders for spreading the seam edges. A transverse fixed arm was located ahead of the arbor and had rollers on its opposite ends for engaging the inner pipe walls. By forcing the pipe over this roller arm the edges were spread without permanent deformation just sufficiently to pass onto the arbor or spreader bar. In the conventional O.D. welder continued pushing of the pipe longitudinally onto the arbor forces the seam edges over fin rollers which assure proper abutment of them as the seam is closed preparatory to welding.
The difficulty with such prior apparatus was that if the pipe was not centered properly before spreading, one or both edges would hit the arbor and prevent passage of the pipe thereon. To correct this, the pipe would have to be moved back off the spreader arm and re-aligned prior to spreading. The conventional roller conveyor could not back the pipe off the arm so it had to be done manually with hooks and a crane. Of course this causes loss of production on the welder and is a safety hazard as well. Moreover, in extreme cases, particularly on softer grades of steel, the seam edges may be overlapped requiring manual prying or jacking of the pipe seam open.
It is therefore a primary object of this invention to provide an improved spreader for a pipe seam welding machine.